Recording switch mechanism



Jyly 22, 1930. T. R. HARRISON I ,9

RECORDING SWITCH MECHANISM I Filed Aug. 27, 1925 INVENTOIR iv (ow I Patented July 22, 1930 UNITED :STATES PATENT OFFICE THOMAS E. HARRISON, PHILADELPHIA, PENNSYLVANIA, ASSIGNOB TO THE BROWN INSTRUMENT COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORA- 1 TION OI PENNSYLVANIA RECORDING SWITCH MECHANISM Application filed August 27, 1925. Serial No. 52,745.

My present invention consists in a novel switch mechanism devised with the general object in view of providing a simple, reliable, and effective mechanism for connecting an '5' electric meter first into one and then into another of a plurality of electric circuits in regular succession. The meter with which the switch may advantageously be used may be a simple indicating instrument, but ordinarily will be a recording or recording and control meter. The invention is especially useful in pyrometric work with the electric circuits into which the meter is connected energized by thermo-couples and with the current creating voltages consequently minute. The invention is characterized by the simplicity in construction and effectiveness in operation of the switch mechanism, and particularly by the provisions made for maintaining the switch contact members in a bath of oil or like liquid which prevents surface oxidation or corrosion of, or dirt accumulations on the switch contact members, and thereby tends to a minimum contact resistance. This is especially advantageous with the low voltages existing in pyromcter circuits, and with the tendency to oxidation, corrosion and dirt accumulations when the instrument is located inan atmosphere containing furnace dust or fumes.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of the specification. For a better under-standing of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descrip tive matter in which I have illustrated and described preferred embodiments of my invention.

Of the drawings:

Fig. 1 is an elevation partly in section of a portion of a meter equipped with my improved switch mechanism;

Fig.2 is an end elevation of the apparatus shown in Fig. 1 with the lower portion of the apparatus in section on the line 22 of Fig. 1;

Fig. 3 is a diagrammatic representation of the meter and circuits with which the switch mechanism may be used; and

juriously-atfected by contact with the oil or other-liquid in which the switch contacts are immersed. Mounted on the lower end of. the part K and extending circumferentially along the periphery of the latter are upper and lower contacts C and D each of which might be a complete circle, but as shown, is an arc of a trifle less than 360. Between the contacts C and D are an upper intermediate set of contacts G, G G and G, corresponding in number to the circuits into which the switch mechanism is to connect the meter and a lower intermediate set of contacts H, H H and H. The contacts G, G G and Gr are arranged in a circular series, each contact being in the form of an arc of slightly less than 90, and the adjacent sections being similarly spaced apart. The contacts H, H H and H are similar in form and relative disposition to the contacts G, G G and G. The various contacts C, D, H, etc., advantageously may each be in the form of a suitably curved length of platinum wire secured nalled in a central tubular boss K depending from the under side of the body K is a shaft I which carries at its upper end a bevel gear in mesh with a bevel gearB carried by an' At its lower end the actuating shaft B shaft I carries a cross head or brush support I on which is mounted a pair of flexible mechart feeding motor.

tallic brushes or spring contact members E and F. As the shaft I-is rotated, the brush E successively connects the contacts G, G G and G with the contact 'C, and the brush F successively connects the contacts H, H, H, and H with the contact D.

The switch supporting body K is formed with a depending flange portion K surrounding the barrel portion K and internally threaded to receive the externally threaded upper end of a cup-shaped container L which is advantageously made of glass, and is filled with oil or other suitable liquid to a level above the contact C and brush E, so that the various contacts and brushes are protected by the liquid against surface oxidation, corrosion, or surface dirt accumulations tending to increase the contactresistance.

- The support K may advantageously be secured to the frame-work of the meter with which the switch mechanism is used. For example, the plates B between which the support K is shown as secured by screws K, may well be the side members of the motor mechanism provided to depress the meter pointer and advance the chart or record strip in such an instrument, as is shown, for example, in the application of Richard P. Brown, Serial No. 756,475, filed December 1, 1924. In such case, the shaft B may be driven through suitable gearing from the pointer depressing and Advantageously, the

a switch supporting member K is provided at the front end of the instrument with a dial swept by a pointer M carried by the end of the shaft B and indicating the position of the brushes E and F relative to the various switch contacts G, G cm, H, H, etc.

Fig. 3 diagrammatically illustrates the use of the switch mechanism shown in Figs. 1 and 2, for successively connecting thermo-couples A, A A and A, to the terminals of the winding of a galvanometer or other meter B provided with a pointer B for impressing on a record chart, records 0, O O and 0,

corresponding to the temperatures to which the thermo-couples A, A A and A are respectively subjected. In Fig. 3 thewlndmg of the meter Bhas one terminal B connected to the contact E, and its other terminal connected to the contact F. One terminal, for example the positive terminal, of the thermocouple -A is connected to the switch contact G while the positive terminals of the thermocouples A2, A, and A are connected, respectively, to the switch contacts G G and G. The other terminals of the thermo-couples A, A A and A are connected to the switch contacts H, H H and H, respectively. As the brushes E and F are diametrically op- .posed,'the contacts G and Hare also diametrically opposed, and the same is true of the contacts G and H, G and H and G and H.

With the described arrangement when the 'switch contacts and brushes.

' increase the pointer M is opposite the numeral 1 on the dial, brush E engages the contact G and the brush F engages the contact H. This connects the thermo-couple A to the meter B, and the pointer B of the latter then indicates the value of the temperature to which the .thermo-couple A is exposed and is in position to make an impression in the record chart line 0' constituting the record of the temperature measured by the thermo-couple A. As the shaft B is rotated to bring the pointer M opposite the dial numeral 2, the brushes E and F are brought into engagement with the contacts G and H respectively, connecting the thcrmo-couple A to the meter B. Similarly as the pointer M passes through the dial positions 3 and 4 the thermo-couples A and A are successively connected to the meter B. The brushes E and F are shown as fiat springs, and preferably'the extent of their contact engaging surface is suflicient to bridge the gaps between the contact sections H, H and H etc., G, G, and G, etc. as well as the gaps between the ends of the contacts C and D so that the current through the meter is not interrupted as the different thermo-couples are successively connected into the meter. This reduces the movement of the meter pointer and eliminates the shocks on the movable element of the meter which would result if the meter circuit were opened in changing from one thermo-couple to the other so that the meter pointer would then return ,to zero.

Those skilled in the art will understand that any one of numerous liquids may be used to form the protective bath for the Ordinarily I prefer to use some relatively thin or non viscous hydrocarbon oil which evaporates at a relatively slow rate and is relatively uninflammable. A practical advantage of the construction illustrated is that with the container L somewhat less than half filled with liquid as indicated, and with the elongated depending hub K at the margin of the opening through the member K for the shaft I, the li uid will not spill out of the'con tainer w en the instrument is tipped over as it may be in mounting it on, or dismount ing it from the instrumentpanel by which it is normally carried. The protective effect of the contact member immersing bath is especially valuable in pyrometry work because pyrometer meters are frequently employed in an atmosphere containing corroding furnace fumes. The protective effect of the contact member immersing bath is especially valuable for use in pyrometers including thermo-couples, because of the small thermo-couple E. M. F. usually less than one tenth of a volt, makes it highly desirable to kee the contact surfaces free from dirt and oxi ized films which tend to vary and unduly switch contact resistance. Trouble from such films is especially apt to occur because pyrometer switches are fre quently exposed to furnace fumes tending to corrode the switch contact surfaces if the latter are not protected as herein provided for. I am aware, of course, of the common use of so called oil switches, but in such switches the switch members are primarily" immersed in oil to minimize arcing. In instrument switches, the voltages employed are operation of the apparatus provided the terminals of the thermo-couples A, A A and A shown in Fig. 3 as connected to the switch contacts G, G G and G", respectively, are directly connected to the corresponding mc ter terminal "13 as shown in Fig.4. \Vhile the arrangement of Fig. 4 is somewhat simpler, I ordinarily prefer in practice to employ the construction shown in Figs. 1 03.

While in accordance with the provisions of the statutes, I have illustrated anddescribed the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims and that in some cases lcertain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is: I

1. In a meter switch mechanism, a supporting structure comprising a depending barrel of insulating material, a vertical shaft axially disposed in said barrel, mechanism carried by said supporting structure including a gear connection to the upper end of said shaft for rotating the latter, a contact carrier secured to the lower end of said shaft circular sets of are shaped meter circuit contacts carried by said barrel and exposed at the periphery thereof,"and contacts supported by said carrier and engaging and disengagingthe different contacts carried by said barrel as said shaft is rotated to thereby successively I energize different meter circuits, a cup-shaped oil container into which said barrel extends,

and means detachably securing said container to said support.

2. In a meter switch mechanism, a supporting structure co'mprisinga depending barrel of insulating material a nd a threaded portion surrounding the upper end of the barrel, 8. vertical shaft axially disposed in said barrel, mechanism carried on said support including a gear connection to the upper end of said shaft forrotating the latter, a contact carrier secured to the lower end of said'shaft, circular sets of are shaped meter circuit contacts carried by said barrel and exposed at the periphery thereof, and contacts supported by said carrier and engaging and disengaging the first mentioned contacts as said shaft is rotated to successively energize different meter circuits, a cup-shaped glass oil container into which said barrel extends, said container having a threaded portion at its upper end in threaded engagement with the thread ed portion of said structure.

3. In a meter switch mechanism,-a supporting structure comprising a depending barrel of insulating material and an internally threadeddepending flange surroundin the upper end of the barrel, a vertical sha axially disposed in sa id barrel, mechanism carried on said support including a gear connection to the upper end of said shaft for rotating the latter, a contact carrier secured to the lower end of said shaft, circular sets of are shaped meter circuit contacts carried by'said barrel and exposed at the periphery thereof, and contacts supported by said carrier and engaging and disengaging the first mentioned contacts'as said shaft is rotated to successively energize different meter circuits, a cupshaped glass oil container into which said barrel extends, said container having its upper end externally threaded and in threaded engagement with said'flan e.

4. In a meter switch mec anism, a supporting structure comprising a depending barrel of. insulating material, a vertical shaft axi-- ally disposed in said barrel, mechanism carried by said supporting structure including a gear-connection to the upper end of said shaft for revolving the latter, a contact carrier secured to the lower end of said shaft, contacts carried by said'carrier, precious metal wires carried by said barrel and forming side b side circular. sets of are shaped meter circuit contacts at the outer surface of said barrel providing tracks along which the first mentioned contacts slide as said shaft is revolved,

'a cup-shaped oil container into which said barrel extends, and means detacha'bly securing-said container to said support. I

Signed at Philadelphia, in the county of Philadelphia and State of Pennsylvania, this 24th day of August. A. D. 1925.

' THOMAS R. HARRISON. 

